qom: Add helper function for getting user objects root

Add object_get_objects_root() function which is a convenience for
obtaining the Object * located at /objects in the object
composition tree. Convert existing code over to use the new
API where appropriate.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>

include/qom/object.h

@@ -1026,6 +1026,18 @@ const char *object_property_get_type(Object *obj, const char *name,
  */
 Object *object_get_root(void);
 
+
+/**
+ * object_get_objects_root:
+ *
+ * Get the container object that holds user created
+ * object instances. This is the object at path
+ * "/objects"
+ *
+ * Returns: the user object container
+ */
+Object *object_get_objects_root(void);
+
 /**
  * object_get_canonical_path_component:
  *

iothread.c

@@ -19,8 +19,6 @@
 #include "qmp-commands.h"
 #include "qemu/error-report.h"
 
-#define IOTHREADS_PATH "/objects"
-
 typedef ObjectClass IOThreadClass;
 
 #define IOTHREAD_GET_CLASS(obj) \
@@ -160,7 +158,7 @@ IOThreadInfoList *qmp_query_iothreads(Error **errp)
 {
     IOThreadInfoList *head = NULL;
     IOThreadInfoList **prev = &head;
-    Object *container = container_get(object_get_root(), IOTHREADS_PATH);
+    Object *container = object_get_objects_root();
 
     object_child_foreach(container, query_one_iothread, &prev);
     return head;

numa.c

@@ -485,7 +485,7 @@ MemdevList *qmp_query_memdev(Error **errp)
     Object *obj;
     MemdevList *list = NULL;
 
-    obj = object_resolve_path("/objects", NULL);
+    obj = object_get_objects_root();
     if (obj == NULL) {
         return NULL;
     }

qmp.c

@@ -651,15 +651,15 @@ void object_add(const char *type, const char *id, const QDict *qdict,
         }
     }
 
-    object_property_add_child(container_get(object_get_root(), "/objects"),
+    object_property_add_child(object_get_objects_root(),
                               id, obj, &local_err);
     if (local_err) {
         goto out;
     }
 
     user_creatable_complete(obj, &local_err);
     if (local_err) {
-        object_property_del(container_get(object_get_root(), "/objects"),
+        object_property_del(object_get_objects_root(),
                             id, &error_abort);
         goto out;
     }
@@ -706,7 +706,7 @@ void qmp_object_del(const char *id, Error **errp)
     Object *container;
     Object *obj;
 
-    container = container_get(object_get_root(), "/objects");
+    container = object_get_objects_root();
     obj = object_resolve_path_component(container, id);
     if (!obj) {
         error_setg(errp, "object id not found");

qom/object.c

@@ -1054,6 +1054,11 @@ Object *object_get_root(void)
     return root;
 }
 
+Object *object_get_objects_root(void)
+{
+    return container_get(object_get_root(), "/objects");
+}
+
 static void object_get_child_property(Object *obj, Visitor *v, void *opaque,
                                       const char *name, Error **errp)
 {